PCO2 CONTROL BY FRESH GAS FLOW DURING CONTROLLED VENTILATION WITH A SEMI-OPEN CIRCUIT

Summary: Investigation was carried out on ten adult patients undergoing abdominal surgery under nitrous oxide, oxygen and alcuronium anaesthesia, using the Mapleson D semi-open system. Ventilation was controlled throughout at a constant ventilation volume of 16 l./min. Pco2 levels varied according to the fresh gas flow. The mean Pco2 was 34.7 (SD 5.7) mm Hg at a fresh gas flow of 8 l./min, 44.2 (SD 6.3) mm Hg at a flow of 4 l./min, 60.2 (SD 9.9) mm Hg at a flow of 2 l./min, and 88 (SD 17.6) mm Hg at a flow of 1 l./min. At normal body temperature, normocarbia will be achieved by a fresh gas flow of about 5 l./min, which is approximately equal to the alveolar ventilation volume of the average adult. © 1969 John Sherratt and Son Ltd.